DE 10 2006 004 120 A1 discloses a hydraulic accumulator, in particular in form of a bladder accumulator, for the purpose of accepting at least one fluid medium within a pressure vessel comprising a first synthetic sheath as well as a second synthetic sheath that at least partially surrounds the first synthetic sheath. The first synthetic sheath is provided at least at its one end with a collar portion, which comprises an opening for a valve that is provided for controlling the media supply and discharge. The collar portion and the second synthetic sheath are supported on an in-between-located outer support ring, which tapers in a wedge-like manner in the direction of a slot-shaped opening between the two sheaths.
In the known solution, the slot-shaped opening between the sheaths is extended to a point where the sheaths are coaxially in contact with each other. In the opening, a poppet valve is disposed for controlling the media supply and discharge. A sealed accumulator arrangement is provided that can be realised at relatively low manufacturing costs. Because the support extends via the wedge-shaped tapered outer support ring into the outer circumference section of both sheaths, any relative movements that may occur between the synthetic sheaths are absorbed by the outer support ring. Damaging delamination processes are directly avoided in this manner between the sensitive synthetic materials.
The technical terminology for the first synthetic sheath is also “synthetic core container” or “liner”. It is preferably made from polyamide by a blow moulding process or through rotational moulding. At the outer circumference the first synthetic core container or liner is reinforced through externally wound fibre windings, which constitutes the second synthetic sheath. To protect the fibre windings, the individual fibres can be embedded in a basic matrix of duromers, for example epoxy resins, phenolic resins or in thermoplastic resins, for example in form of PA6, PA12, PP etc. In order to place the poppet valve, i.e. the valve for liquids, on the one side of the accumulator housing, as well as the gas supply valve on the other opposite side of the accumulator housing, relatively large openings are required in the two-sheath accumulator housing, into which openings the respective collar portions must be placed in order to secure the respective valve at its housing opening side.
DE 10 2011 111 098 A1 discloses a pressure vessel, which is preferably used for bladder accumulators, comprising a multi-part container body that includes a tube-like centre section providing at least on one of its two ends an end section. A cover, which forms at least in part the respective end section, overlaps the centre section at the edge at least in the section of its respective end and forms a solid connection.
The known solution proposes to form the tube-shaped centre section as well as the respective cap from a fibre-reinforced composite material and/or from a fibre laminate, preferably from a glass fibre reinforced plastic (GRP). Standard GRP pipes can be used for the centre section. The caps for closing off said centre section are preferably made by a manual lamination process and may have comparable synthetic materials.
At the cap end of the accumulator housing, which will later accommodate the valve for the liquid, a relatively large opening is provided. That opening permits the accumulator bladder as the bladder body to be drawn, together with the gas filling valve that is attached through vulcanising, into the inside of the accumulator housing so that the gas valve is located on the opposite side of the housing in the respective opening in the accumulator housing that has a comparatively smaller diameter. With regard to the different sizes of the valve openings in the accumulator housing, the subsequently applied windings are different by necessity. Each individual winding will have a different formation when subsequently combined, in particular with regard to its wall diameter, so that, although the composite fibre layers can be simply wound, when forces are applied weak points become apparent, in particular when it is desired to achieve high strength values in axial direction of the accumulator housing.